Some recent charged particle beam devices, such as a transmission electron microscope (TEM) and a scanning transmission electron microscope (STEM) include a spherical aberration correction device (hereinafter referred to as an aberration corrector). This aberration corrector is used for correcting a spherical aberration (Cs) of an objective lens which is a main factor limiting resolution in the TEM and the STEM. Known as the aberration corrector is the one which has two multi-pole lenses generating a six-pole field and two axisymmetrical lenses (transmitting lenses) arranged therebetween (for example, see Patent Literature 1).
The Cs of the objective lens is corrected by the aberration corrector. However, due to incompleteness of the aberration corrector, that is, for example, a position aberration of individual poles forming the multi-pole lens and magnetic property variation of a pole material, unnecessary aberrations called parasitic aberrations occur. The occurring third or lower parasitic aberrations include: a two-fold symmetric primary astigmatism (A1), a one-fold symmetric secondary coma aberration (B2), a three-fold symmetric secondary astigmatism (A2), a two-fold symmetric third star aberration (S3), and a four-fold symmetric third astigmatism (A3). In adjustment of the aberration corrector, correction of these parasitic aberrations in addition to the Cs is necessary.
To an aberration corrector of a product, an alignment tool for correcting the Cs and the parasitic aberrations are attached, and an adjustment staff member can use the alignment tool to semi-automatically perform adjustment of the aberration corrector (for example, see Non-Patent Literature 1). Arranged on GUI (graphical user interface) of the alignment tool are: an aberration measurement button, and aberration correction buttons respectively corresponding to a plurality of aberrations. As a result of pressing the aberration measurement button, an aberration coefficient representing magnitude of each aberration remaining in the optical system is measured based on a plurality of obtained electroscopic images (for example, see Patent Literature 2 for an aberration measurement method). As a result of pressing the aberration correction button, a feedback acts on the aberration corrector in accordance with the measured aberration coefficient, and the specified aberration is corrected (for example, see Patent Literatures 3 and 4 for an aberration correction method).
The aberration measurement and correction are automatically performed by the use of the alignment tool, but judgment on which aberration is to be preferentially corrected based on a result of the aberration measurement is left up to the adjustment staff member. Normally, the adjustment staff member corrects the aberrations preferentially starting with the aberration with the largest aberration coefficient, and the correction is repeated until all the third or lower aberrations become equal to or smaller than a permitted value.
Disclosed in a field of an optical disc device is a method of learning an optimum control amount for aberration correction (recording an optimum status found through searching) (see Patent Literature 5).